Turn a Calculator Into a Metal Detector

Introduction: Turn a Calculator Into a Metal Detector

I recently discovered a really cool method in using a few household items to make a HomeMade Metal Detector! Heres how to make your own!

Heres a link to the video : http://www.youtube.com/watch?v=_G5HzeIl9cY

Step 1: What You Need.

All you need for this project is, an: AM Radio , some tape , and a small calculator.

Step 2: Let's Begin

Begin by turning the AM radio on. Tune it to the high end of the AM band, but not directly on a broadcast station. Adjust the volume to the maximum level so you can clearly hear the static.

Step 3: Positioning It

Now with both the calculator and the radio turned on, position the calculator close to the radio till you hear a loud tone

Step 4: Taping It Together

Once, this position is found, tape the calculator to the radio while maintaining the placement.
When you done taping it together, make sure its steady.

Now lets test it out.

Step 5: Testing It Out

Turn your radio on, and try the metal detector out on any type of metal. You will notice that the calculator beeps whenever you get close to metal. It beeps even faster the closer you get to the metal.

Step 6: Why It Works

The reason this works is because the loud tone coming from the radio is the calculators
electronic circuit producing a radio frequency signal. That being said, the radio waves from the calculator reflect off the spoon and are heard on the AM radio.

And there you have it, A cheap and easy homemade metal detector.

Enjoy, and have fun!

PS: If you like this instructable, please give it a nice rating. Thanks!

I tried making this detector a lot of different ways e.g. calc and radio back to back, with an angle between them using a cd case etc and have had no luck with it at all. I notice that a couple of people - like ridge2244 10 months ago said that it worked. What make of radio and calculator actually work together? Also does the beeping really speed up as the metal gets nearer to the radio? If I'm honest, I am feeling pretty sceptical about it at this stage! Has anyone else got it to work? If so, I'd love to hear which calc and radio you used and how you positioned them.

"You will notice that the calculator beeps whenever you get close to metal. It beeps even faster the closer you get to the metal. "

This was my first clue that this makes no sense at all. What would possibly induce the calculator to beep in the presence of a metal. Surely it would do so whether it had a radio strapped to its back or not. Never seen one do that yet.

If it worked at all it would have to relate to signal strength received by the radio due to reflection or eddy current losses as the radiated noise approaches the metal. Then maybe there would be a barely audible change. It would be nice if there was some Beat Frequency or Heterodyne effect, but since the radio is not "Tuned" to the calculator's oscillator or any thing like that this is unlikely. This does appear to happen when buttons are pressed as has been mentioned by others, and that is not a surprise.

SergentLaughter, Try taping one or more of your calculator buttons down, that should do it ;) Oh ya, RazorG606, nice idea but it is already all over the net. Another Thing is that yes it is a metal detector, but the range of this project is too small for anything other than finding coins in the sofa and studs in the wall. But still, if you hacked the radio to give more reception and then put aluminum in the calculator, then put a faraday sheild in between the two devices, the range should increase enough to match a full scale one. P.S. If you try to make the excuse that I do not know what I am talking about, you should know that I did your project a billion times (maybe not a billion, but close enough) and I'm a jack-of-most trades. Meaning, I can make or repair ANYTHING you can THINK of. So that being said, hope you take my advice, at least with the faraday shielding. That should make the most diference in range. I hope by the time you get to the end of my comment, you do not take offence of my p.s.. You see, people seem to think i'm stupid and a was just clarifying the reverse of that. Hope to talk soon, For Better or Worse

And just to clarify before the trolls jump on this and attempt to disprove things based on one small formality..

http://preview.tinyurl.com/3ltb6ng

(you notice I gave you the preview of that url, that's cause I know how ppl are with redirector sites, so before you say Hurr Durr, just check em)

The TI-108 unit is solar powered and does not use a battery to power it. (from TI's knowledge base)

So no that calc in the video DOES NOT have a battery. Still, it is able to use the ambient light (carpet doesn't have to be 'reflective' for light to be available in the room, as a matter of fact, solar calculators require very little power) in the room to function.. How amazing is that?

Thanks for the good info.I published a website that has guides to making a more advanced pulse induction metal detector based on the same technology found in minelabs gpx series gold detectors. It's really easy to build and I'd defiantly recommend it to someone who has some electrical skill.http://www.miymd.com

Oh ya, RazorG606, I forgot to mention that if you are interested in stuff like this, Try Making my analog Transmitter from random things. It needs some improvements, like faraday shielding. Hope you leave plenty of comments for me.. One other thing, if you do not know what a faraday shield is, it is usually a steel sheet or mesh that is grounded to the negative of the battery terminal or is earthed. Hope this helps. For Better or Worse...

of course, there is no video here at this site. but if you go to www.metacafe.com, you can see the full length video of this prank. Please do yourselves a favor, watch the video, take a good look at him passing the metal detector over the spoon.